amethyst/.claude/CLAUDE.md

Amethyst

Project Overview

Amethyst is a Nostr Client for Android that was made for Android-only and has been slowly switching over to a Kotlin Multiplatform project. The main modules are: quartz, commons, commonsUI, amethyst, desktopApp, cli, plus the audio-rooms transport stack quic + nestsClient. Quartz should contain implementations of Nostr specifications and utilities to help implement them. Commons stores shared code between Amethyst Android (amethyst) and Amethyst Desktop (desktopApp). The Desktop App is designed to be mouse first and so uses a completely different screen and navigation architecture while sharing the back end components with the android counterpart. cli ships amy, a non-interactive JVM command-line client that drives the same quartz + commons code — used by humans, agents, and interop tests. quic is a from-scratch pure-Kotlin QUIC v1 + HTTP/3 + WebTransport client (no JNI, no BouncyCastle), built because no Android-compatible Java QUIC library exists. geode is a standalone JVM Nostr relay (Ktor) built on quartz's relay-server code; smaller modules are benchmark (Android macrobenchmarks), relayBench (head-to-head relay benchmark — boots geode, strfry and other relay binaries, replays a shared deterministic corpus, measures ingest/query/ NIP-77 sync; ./relayBench/run.sh, see relayBench/README.md) and quic-interop (QUIC interop runner, lives at quic/interop). marmotQuic is the Marmot raw-QUIC transport binding for agent text stream previews (transports/quic.md) on top of :quic — its own ALPNs and framing, not WebTransport. nestsClient runs the audio-room protocol on top of :quic for the NIP-53 audio-rooms feature. It implements both IETF draft-ietf-moq-transport-17 (under moq/) and moq-lite Lite-03 (kixelated's variant, under moq/lite/); the production listener AND speaker paths both run on moq-lite to interop with the nostrnests reference relay. The IETF code is kept as a reference + unit-test implementation for any future IETF target; see nestsClient/plans/2026-04-26-moq-lite-gap.md.

Canonical NIP specs live at https://github.com/nostr-protocol/nips — use /nip <number> to pull a specific one (it fetches the spec file directly).

Verify, Don't Guess

Don't assert a diagnosis you haven't reproduced. This repo gives you cheap verification tools: ./gradlew test, per-module test suites, and the amy CLI (built partly to drive quartz/commons for interop checks). If a claim is checkable in under a minute, check it before stating it — write the failing case first, watch it fail, then explain.

Architecture

amethyst/
├── quartz/         # Nostr KMP library (protocol only, no UI)
│   └── src/
│       ├── commonMain/    # Shared Nostr protocol, data models
│       ├── androidMain/   # Android-specific (crypto, storage)
│       ├── jvmMain/       # Desktop JVM-specific
│       └── iosMain/       # iOS-specific
├── commons/        # Shared HEADLESS layer (models, state, ViewModels, relay client) — CLI-safe
│   └── src/
│       ├── commonMain/    # Domain models, state holders, ViewModels, services
│       ├── jvmAndroid/    # JVM-bound services shared by Android + Desktop
│       ├── androidMain/   # Android-specific actuals (Keystore, DataStore)
│       └── jvmMain/       # Desktop-specific actuals (keyring, upload pipeline)
├── commonsUI/      # Shared Compose UI on top of commons (composables, icons, theme, Coil, resources)
│   └── src/
│       ├── commonMain/    # Shared composables, icons, theme, composeResources (strings/fonts)
│       ├── jvmAndroid/    # Markdown renderer, Coil OkHttp fetchers
│       ├── androidMain/   # Android Coil bridge
│       └── jvmMain/       # Desktop Coil bridge (+ skikoMain shared with iOS)
├── quic/           # Pure-Kotlin QUIC v1 + HTTP/3 + WebTransport (audio-rooms transport)
│   └── src/
│       ├── commonMain/    # Protocol, frame/packet codecs, TLS state machine
│       ├── jvmAndroid/    # JCA-backed AEAD + UDP socket actuals
│       └── commonTest/    # RFC vector + adversarial tests
├── nestsClient/    # Audio-room client (production runs on moq-lite; IETF MoQ kept as reference)
│   └── src/
│       ├── commonMain/    # MoQ session, NestsListener, audio glue
│       └── jvmAndroid/    # Opus encode/decode, AudioRecord/AudioTrack
├── geode/          # Standalone JVM Nostr relay (Ktor) on quartz's relay-server code
├── desktopApp/     # Desktop JVM application (layouts, navigation)
├── amethyst/       # Android app (layouts, navigation)
└── cli/            # Amy — non-interactive CLI (JVM only, no Compose)

Sharing Philosophy:

• quartz/ = Nostr business logic, protocol, data (no UI)
• commons/ = Shared headless code for every front end (Android, Desktop, iOS, and the headless cli): domain models, state holders, ViewModels, the relay client, shared services. It may use the Compose runtime (@Stable/@Immutable, snapshot state) but never Compose UI, Coil or Compose resources — the build enforces this: commons has no such deps.
• commonsUI/ = Shared Compose UI that ≥1 GUI front end renders (composables, ui/theme, icons, robohash, Coil fetchers, markdown, the composeResources strings/fonts and the generated Res class). Depends on commons (as api); cli never depends on it. Files keep their com.vitorpamplona.amethyst.commons.* packages — the split is a module boundary, not a package rename. The package taxonomy, the CLI-safe / UI boundary, and a "where does my code go?" guide are documented in commons/ARCHITECTURE.md (+ commonsUI/ARCHITECTURE.md) — read them before adding a new package or dropping code into either module.
• quic/ = Transport library (QUIC + HTTP/3 + WebTransport); reusable for any KMP project that needs MoQ. Has no Android-framework dependencies.
• nestsClient/ = MoQ + audio-rooms client; takes :quic as transport, Quartz for crypto, MediaCodec / AudioRecord / AudioTrack for audio.
• marmotQuic/ = Marmot's raw-QUIC binding for agent text stream previews. Takes :quic for the connection and :quartz for the record/envelope codecs. Not WebTransport — the binding has its own ALPNs and writes frames straight onto QUIC streams, so it deliberately does not reuse nestsClient's WebTransportSession.
• amethyst/ & desktopApp/ = Platform-native layouts and navigation
• cli/ = Thin assembly layer over quartz/ + commons/ (no new logic allowed). May also depend on :geode (for amy serve, which embeds the standalone relay); never on :commonsUI, :amethyst or :desktopApp.

Plans per module: design docs for new subsystems live in the owning module's plans/YYYY-MM-DD-<slug>.md (e.g. cli/plans/, commons/plans/). The global docs/plans/ folder is frozen — don't add new plans there.

Android Runtime Processes (IMPORTANT — the app runs in TWO processes)

The Android app is not single-process. Android instantiates the one Amethyst Application class (there is no per-process Application in the manifest) in both:

• main — the normal app: UI, account, signer, LocalCache, relay client. Amethyst.instance (AppModules) is built here.
• :napplet — the sandboxed WebView host for NIP-5D napplets / NIP-5A nSites (NappletHostActivity, declared android:process=":napplet"). It holds no account or keys; Amethyst.onCreate() early-returns here so Amethyst.instance is left unset (touching it throws UninitializedPropertyAccessException). The sandbox runtime lives in its own module :nappletHost (depends only on :commons + :quartz, never :amethyst) so it cannot import Amethyst/LocalCache/Account — the broker-side (signer, gateways, registry) stays in :amethyst and the two halves talk over Messenger IPC.

Consequences — don't get caught assuming one process:

• Processes don't share memory. Every object/companion/static is a separate copy per process: LocalCache (an object), NappletLaunchRegistry, etc. The populated LocalCache lives only in main; the sandbox neither builds nor should reference it (a stray reference would lazily create a second, empty cache there).
• Don't assume Amethyst.instance exists. Any code reachable from :napplet (the host activity, content server, or an Application lifecycle callback like onTrimMemory) must guard on the process and never reach for instance.
• Cross-process state goes over Messenger IPC, never a shared singleton — this is why the broker (main) owns NappletLaunchRegistry and the sandbox only relays an opaque token. See amethyst/plans/2026-06-22-napplet-nsite-security.md.

Tech Stack

Exact versions live in gradle/libs.versions.toml (the source of truth — check there rather than trusting a number copied here).

Layer	Technology
Core	Quartz (Nostr KMP)
UI	Compose Multiplatform
Async	kotlinx.coroutines + Flow
Network	OkHttp (JVM)
Serialization	Jackson
DI	Manual / Koin
Build	Gradle + Kotlin Multiplatform

Skills

The full list of available skills (with descriptions and triggers) is injected into every session, so it isn't duplicated here. Two kinds exist and are meant to be used together:

• Codebase-oriented skills (nostr-expert, compose-expert, feed-patterns, account-state, amy-expert, …) answer "where is X in Amethyst, what pattern do we use here."
• Technique-oriented skills (vendored from chrisbanes/skills, e.g. compose-slot-api-pattern, kotlin-flow-state-event-modeling) answer "what is the correct Compose/Kotlin design." They complement, not replace, the codebase skills: compose-expert tells you where shared composables live; compose-slot-api-pattern tells you how to shape their public API.

Feature Workflow

CRITICAL: Check existing implementations first — most logic already exists. Before writing code, survey all modules (use Grep/Explore) for managers, caches, state systems, filters, ViewModels, and composables that already do the job. Your job is usually to reuse (quartz protocol/business logic), extract (Android UI/ViewModels → commons), and add platform-specific layouts/nav — not to duplicate existing managers, caches, or state.

Summarize the survey in your plan: for each component, note whether it's reused as-is, extracted from amethyst/ to commons/, genuinely new (platform-specific only), or a duplicate of an existing pattern to avoid.

Relay client ops already exist — don't hand-roll subscribe/REQ/publish loops. One-shot and high-level relay operations (fetch a set, fetch one, page past the relay cap, publish-and-confirm, NIP-45 count, NIP-77 sync/reconcile) are INostrClient extension functions in quartz/…/nip01Core/relay/client/accessories/ (+ …/reqs/ for the flow/subscribe helpers). Because they're extensions, they don't surface under "usages of NostrClient" or in completion — grep that package (or read its README.md, which catalogs them) before writing a new subscription/collect loop. Reuse fetchAll, fetchFirst, fetchAllPages, publishAndConfirm, count, negentropyReconcile, etc. instead of re-implementing them.

Share vs keep platform-native:

• Share → quartz/commonMain/ (business logic, data models, protocol), commons/commonMain/ (ViewModels under viewmodels/, state holders, relay client, services — headless) and commonsUI/commonMain/ (major UI components, icons, theme). ViewModels are platform-agnostic state + logic (StateFlow/SharedFlow), so they belong in commons; anything that imports androidx.compose.ui/foundation/material3, Coil, or Res belongs in commonsUI.
• Keep native → screen composables/scaffolding (Desktop Window vs Android Activity), navigation (sidebar vs bottom nav), platform interactions (gestures, keyboard shortcuts), system integrations (notifications, file pickers).

When extracting a composable: move it to commonsUI/commonMain/ (see /compose-expert), add expect/actual for any platform behavior (see /kotlin-multiplatform), then point both Android and Desktop at the shared version. quartz/ is protocol-only — no composables.

Build Commands

# Run desktop app
./gradlew :desktopApp:run

# Run Android app
./gradlew :amethyst:installDebug

# Build Quartz for all targets
./gradlew :quartz:build

# Run tests
./gradlew test

# Format code
./gradlew spotlessApply

Dependency Licensing

MANDATORY whenever you introduce a new third-party dependency — in any module (quartz, commons, commonsUI, amethyst, desktopApp, cli, quic, nestsClient, …), whether you add it to gradle/libs.versions.toml or to a module's build.gradle.kts: determine its license before wiring it in. Amethyst ships under the MIT license, so a copyleft dependency linked into a distributed artifact (APK, desktop binary) can force that artifact's combined-work terms onto the whole project.

Verify against the dependency's actual LICENSE/COPYING file or its published POM — not from memory. Then classify and act:

• Permissive (MIT, Apache-2.0, BSD, ISC, MPL-2.0, zlib, …) → OK, proceed.
• LGPL, or GPL/EPL with a linking / Classpath exception → WARN. Acceptable to link (the exception keeps our own code MIT), but call it out in your summary so the human knows. Confirm the exception actually exists in the LICENSE text — don't assume it does.
• Stricter than LGPL — GPL/AGPL without a linking exception, SSPL, proprietary/commercial-only, or anything where the linking-exception check is "no" → STRONGLY WARN and STOP. Do not add it silently. Surface it prominently and require an explicit call-out in the PR description so a maintainer makes the decision. Prefer a permissive alternative, a clean-room implementation, or dropping the feature.

For any GPL-family hit the decisive question is always "is there a linking (LGPL/Classpath) exception?" — that is what separates a WARN from a STOP. (Example: TarsosDSP, GPLv3 with no exception, was removed from amethyst and replaced with an in-house pitch shifter for exactly this reason.)

Quartz KMP Structure

Quartz uses expect/actual for platform-specific implementations (e.g. crypto backed by secp256k1-kmp-jni-android on Android and secp256k1-kmp-jni-jvm on JVM). See /kotlin-multiplatform for the expect/actual and source-set patterns.

Icons

The Material Symbols font bundled at commonsUI/src/commonMain/composeResources/font/material_symbols_outlined.ttf is a subset that only contains the glyphs referenced from commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/MaterialSymbols.kt.

MANDATORY: Whenever you add a new icon — i.e. introduce a MaterialSymbol("\uXXXX") codepoint that wasn't already referenced anywhere in MaterialSymbols.kt — you MUST regenerate the subset font by running:

./tools/material-symbols-subset/subset.sh

Commit the regenerated material_symbols_outlined.ttf alongside your MaterialSymbols.kt change. Without this step the new icon renders as tofu (□) at runtime because the glyph is not in the bundled font.

Reusing a codepoint already present in MaterialSymbols.kt does NOT require regenerating.

Amethyst's own icons are also a font

The icons in commonsUI/.../commons/icons/*.kt (Like, Reply, Reposted, Zap, …) are also compiled into a font, composeResources/font/amethyst_icons.ttf, and drawn as glyphs via AmethystIconGlyph. Drawing an ImageVector rasterises its paths into a per-instance cached layer, so a feed re-rasterised the same glyph once per card; a glyph is a blit from the shared text atlas. Measured: frame P90 -10.7%, overrun P90 -17.4% on the feed scroll benchmark.

MANDATORY: whenever you add or change an icon under commonsUI/.../commons/icons/, regenerate the font and its codepoint table together:

python3 tools/icon-font/build_icon_font.py \
  commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons \
  commonsUI/src/commonMain/composeResources/font/amethyst_icons.ttf \
  commonsUI/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/icons/symbols/AmethystIcons.kt

Both outputs must be committed together: codepoints are assigned in filename order, so adding an icon renumbers the ones after it, and a stale AmethystIcons.kt then points at the wrong glyph. Needs fonttools (pip install fonttools). The script prints any icon it could not convert — an icon that is skipped must keep using its ImageVector. See tools/material-symbols-subset/README.md for details and prerequisites (pip install fonttools brotli).

Code Formatting

After completing any task that modifies Kotlin files, always run:

./gradlew spotlessApply

Do this before considering the task complete.

Kotlin Style

• Never write fully-qualified class names inline in function bodies. Add an import for the class and reference it by its simple name. Write Event (with import com.vitorpamplona.quartz...Event), not com.vitorpamplona.quartz...Event in the middle of code.
• The only acceptable inline fully-qualified names are: a genuine name collision (prefer import ... as Alias instead), or where the language requires it. Comments, KDoc, and string literals are exempt.
• Prefer the androidx.core KTX extension over the raw platform Java call when one exists — this is what Android Lint's UseKtx flags. Common swaps: Bitmap.createBitmap(w, h, cfg) → createBitmap(w, h), Bitmap.createScaledBitmap(src, w, h, f) → src.scale(w, h, f), Uri.parse(s) → s.toUri(), and prefs.edit()…apply() → prefs.edit { }. Only adopt the KTX form when it's behaviour-preserving: keep any explicit argument that differs from the extension's default (a non-ARGB_8888 Bitmap.Config, scale(filter = false)), and leave calls the KTX has no equivalent for (e.g. the createBitmap pixels/matrix overloads, or a conditional-apply() editor loop) untouched.
• This "prefer the KTX sugar" rule does NOT extend to collection operators. The KTX preference is about platform wrappers (Bitmap/Uri/SharedPreferences), which compile to the identical call. Collections are the opposite: in hot event/parse paths Quartz deliberately uses raw JVM arrays (TagArray = Array<Array<String>>) and the inline fast* operators (fastForEach, fastAny, fastFirstOrNull, fastFirstNotNullOfOrNull, … in nip01Core/core/TagArray.kt) instead of Kotlin List + stdlib forEach/map/filter/any — the fast* variants allocate no iterator, no intermediate list, and no lambda object. Don't "modernize" those into stdlib collection calls; match the surrounding hot-path style.
• Never put raw invisible/bidirectional Unicode characters in source files — write them as \uXXXX escapes instead ('\u202E', Regex("[\u200B-\u200D\uFEFF]")). This covers the bidi family Sonar's Trojan-Source rule (CVE-2021-42574) flags — U+202A–U+202E, the isolates U+2066–U+2069, U+200E/U+200F, U+061C — plus zero-width characters (U+200B–U+200D, U+FEFF, U+2060). The escape compiles to the identical codepoint, so behaviour is unchanged; the point is that the file on disk stays visually unambiguous. Applies even when the character is intentional (sanitizer strip-lists, adversarial test payloads) — that's data, and escapes express it just as well. Exceptions: U+200D as part of a real emoji ZWJ sequence in test data (👩‍👧 — functional, not a bidi control), and LRM/RLM inside Crowdin-managed strings.xml translations (legitimate RTL typography; don't touch those files by hand anyway). Note the tooling trap: the Edit tool may normalise a typed \uXXXX back into the raw character — if that happens, do the replacement at byte level (perl -CSD -pe 's/\x{202E}/\\u202E/g').

Navigation Shell

• Desktop: Sidebar + main content area
• Android: Bottom navigation

Git Workflow

• Commits: Conventional commits (feat:, fix:, etc.)
• Never use --no-verify

Remotes & pull requests

A PR can be published two ways, via two kinds of remote — identify them by URL (git remote -v), because the names vary per clone and a collaborator may have only one:

• a GitHub remote (github.com/vitorpamplona/amethyst) — the canonical main; moves constantly. Standard gh PR flow.
• a git-over-nostr remote (nostr://…/relay.ngit.dev/amethyst, via ngit) — pushing fans out to GitHub and the GRASP git servers; PRs here are nostr proposals (the pr/feat/* branches), reviewed on gitworkshop.dev — not GitHub PRs. (In the maintainer's checkout these happen to be named upstream and origin respectively, but don't rely on that.)

Before opening, revising, or merging a PR by either path, use the ngit-pr skill. It covers when to use which, identifying your remotes by URL, the gh and ngit commands, and — critically for the nostr path — the three-mains alignment gate (GitHub main vs the lagging nostr main vs local main) that its create/revise/merge flows depend on. Skipping it leads to rejected pushes and PRs that don't show up as revisions.